In color reproduction in multi-color printing, different printing methods and printing systems as well, for example printers from different manufacturers and printing conditions, lead to different printed results. This means that, given the same driven color data (generally, surface coverage degrees CMYK), the colors that result in the printing often deviate substantially from one another. Often, however, the colors should not only correspond well to the original but should also coincide with the result that is obtained given a different printing method (or, respectively, printing system, printing conditions).
Examples of multiply employed data are:
Printing a small advance press run in addition to a large main press run.
Printing reprints when editions are out of print.
Newspaper notices wherein different printing systems and different papers are employed; here, too, the images should look the same.
The significant causes of the deviations are differences in the primary colors employed. Deviations in the tonal value transmission properties additionally play a part.
Up to now, the above problem was mainly solved by manual corrections of the image data or with color management systems. In color management, the printing system to be characterized is brought into a defined condition and the color transmission properties are then determined by measurement (printing and analyzing specific test patterns). Allocation tables between resulting colors (for example, CIELAB colors) and degrees of surface coverage can be determined therefrom. This allocation can be employed for converting later color data into degrees of surface coverage (Homann, Jan-Peter, Digitales Colormanagement: Farbe in der Publishing-Praxis, Berlin, Springer Verlag, 1998).
Disadvantages of these methods are that
the allocation tables can only be applied for one status (printing conditions, material to be printed);
all image data must be converted device-independently; given printout on different printing systems, another adaptation of the complete dataset is respectively required. In addition to the considerable computing expense, it is especially disadvantageous that it must be assured that the device-dependent color allocations must be co-managed; and
the determination of the allocation tables is only possible with the assistance of expensive measuring technology and software.